straight geodesic
There is an issue with straight geodesics not being computed correctly
```python
T = HyperbolicTiling(3,7,2)
T.generate()
fig, ax = plt.subplots(figsize=(8,8), dpi=100)
for poly in T: # loop over polygons
for i in range(T.p): # loop over vertices
z1 = poly.verticesP[i] # extract edges
z2 = poly.verticesP[(i+1)%T.p]
arc = geodesic_arc(z1,z2,lw=0.6) # compute arc
plt.gca().add_patch(arc) # add to plot
plt.xlim(-bnd, bnd); plt.ylim(-bnd, bnd);
plt.axis("off"); plt.gca().set_aspect('equal')
plt.tight_layout(); plt.show()
```
issue